From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with SMTP id 1F0708D003B for ; Fri, 8 Apr 2011 04:44:14 -0400 (EDT) Date: Fri, 8 Apr 2011 16:44:09 +0800 (CST) From: bill Message-ID: <114cbfb0.1855c.12f34486272.Coremail.bill_carson@126.com> Subject: Query about __unmap_hugepage_range MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: linux-mm@kvack.org Hey, MM developers:) I don't know if this posting is proper at here, so sorry for disturbing if it does. for normal 4K page: in unmap_page_range 1: tlb_start_vma(tlb, vma); <------ call flush_cache_range to invalidate icache if vma is VM_EXEC 2: clear pagetable mapping 3: tlb_end_vma(tlb, vma); <-------- call flush_tlb_range to invalidate unmapped vma tlb entry for hugepage: in __unmap_hugepage_range 1: clear pagetable mapping 2: call flush_tlb_range(vma, start, end); to invalidate unmapped vma tlb entry I really don't understand about two things: A: why there is no flush_cache_range for hugepage when we do the unmapping? B: How does kernel take care of such case for both normal 4K page and hugepage: a: mmap a page with PROT_EXEC at location p; b: copy bunch instruction into p ,call cacheflush to make ICACHE see the new instruction; c: run instruction at location p, then unmap it; d: mmap a new page with MAP_FIXED/PROT_EXEC at location p, and run unexpected instruction at p; there is a great chance we got the same page at step_a; user space should see a clean icache, not a stale one; I am really puzzled for a long time. I am porting hugepage for ARM ,and one testcase in libhugetlbfs called icache-hygiene failed, test rationale is described in above B. Any tips/advice would be truly appreciated. Thanks -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org